The Document Class is in most cases the result of a parsing process. But
sometimes it is necessary to create a Document from scratch. The DOM Document
Class provides functions that conform to the DOM Core naming style.

It inherits all functions from XML::LibXML::Node as specified in the DOM specification. This enables access to the nodes besides
the root element on document level - a DTD for example. The support for these nodes is limited at the moment.

While generally nodes are bound to a document in the DOM concept it is
suggested that one should always create a node not bound to any document. There
is no need of really including the node to the document, but once the node is
bound to a document, it is quite safe that all strings have the correct
encoding. If an unbound text node with an ISO encoded string is created (e.g.
with $CLASS->new()), the toString function may not return the expected result.

To prevent such problems, it is recommended to pass all data to XML::LibXML
methods as character strings (i.e. UTF-8 encoded, with the UTF8 flag on).

Returns the URI(or filename) of the original document. For documents obtained
by parsing a string of a FH without using the URI parsing argument of the
corresponding parse_* function, the result is a generated string unknown-XYZ where XYZ is some
number; for documents created with the constructor new, the URI is undefined.

The value can be modified by calling setURI method on the document node.

setURI

$doc->setURI($strURI);

Sets the URI of the document reported by the method URI(see also the URI
argument to the various parse_* functions).

returns the encoding in which the XML will be returned by $doc->toString().
This is usually the original encoding of the document as declared in the XML
declaration and returned by $doc->encoding. If the original encoding is not
known (e.g. if created in memory or parsed from a XML without a declared
encoding), UTF-8 is returned.

This method allows one to change the declaration of encoding in the XML
declaration of the document. The value also affects the encoding in which the
document is serialized to XML by $doc->toString(). Use setEncoding() to remove
the encoding declaration.

This function returns the Numerical value of a documents XML declarations
standalone attribute. It returns 1if standalone=yes was found, 0if standalone=no was found and -1if standalone was not specified (default on creation).

setStandalone

$doc->setStandalone($numvalue);

Through this method it is possible to alter the value of a documents standalone
attribute. Set it to 1 to set standalone=yes, to 0 to set standalone=no or set it to -1 to remove the standalone attribute from the XML declaration.

compression

my $compression = $doc->compression;

libxml2 allows reading of documents directly from gzipped files. In this case
the compression variable is set to the compression level of that file (0-8). If
XML::LibXML parsed a different source or the file wasnt compressed, the
returned value will be -1.

setCompression

$doc->setCompression($ziplevel);

If one intends to write the document directly to a file, it is possible to set
the compression level for a given document. This level can be in the range from
0 to 8. If XML::LibXML should not try to compress use -1 (default).

Note that this feature will only work if libxml2 is compiled with zlib support and toFile() is used for output.

toString

$docstring = $dom->toString($format);

toString is a DOM serializing function, so the DOM Tree is serialized into an XML
string, ready for output.

IMPORTANT: unlike toString for other nodes, on document nodes this function
returns the XML as a byte string in the original encoding of the document (see
the actualEncoding() method)! This means you can simply do:

regardless of the actual encoding of the document. See the section on encodings
in XML::LibXML for more details.

The optional $format parameter sets the indenting of the output. This parameter is expected to be an integer value, that specifies that indentation should be used. The format parameter can
have three different values if it is used:

If $format is 0, than the document is dumped as it was originally parsed

If $format is 1, libxml2 will add ignorable white spaces, so the nodes content
is easier to read. Existing text nodes will not be altered

If $format is 2 (or higher), libxml2 will act as $format == 1 but it add a
leading and a trailing line break to each text node.

libxml2 uses a hard-coded indentation of 2 space characters per indentation
level. This value can not be altered on run-time.

An alias for toString(). This function was name added to be more consistent
with libxml2.

serialize_c14n

An alias for toStringC14N().

serialize_exc_c14n

An alias for toStringEC14N().

toFile

$state = $doc->toFile($filename, $format);

This function is similar to toString(), but it writes the document directly
into a filesystem. This function is very useful, if one needs to store large
documents.

The format parameter has the same behaviour as in toString().

toFH

$state = $doc->toFH($fh, $format);

This function is similar to toString(), but it writes the document directly to
a filehandle or a stream. A byte stream in the document encoding is passed to
the file handle. Do NOT apply any :encoding(...) or :utf8PerlIO layer to the filehandle! See the section on encodings in XML::LibXML for more details.

The format parameter has the same behaviour as in toString().

toStringHTML

$str = $document->toStringHTML();

toStringHTML serialize the tree to a byte string in the document encoding as HTML. With this
method indenting is automatic and managed by libxml2 internally.

serialize_html

$str = $document->serialize_html();

An alias for toStringHTML().

is_valid

$bool = $dom->is_valid();

Returns either TRUE or FALSE depending on whether the DOM Tree is a valid
Document or not.

You may also pass in a XML::LibXML::Dtd object, to validate against an external DTD:

This is an exception throwing equivalent of is_valid. If the document is not
valid it will throw an exception containing the error. This allows you much
better error reporting than simply is_valid or not.

Again, you may pass in a DTD object

documentElement

$root = $dom->documentElement();

Returns the root element of the Document. A document can have just one root
element to contain the documents data.

Optionally one can use getDocumentElement.

setDocumentElement

$dom->setDocumentElement( $root );

This function enables you to set the root element for a document. The function
supports the import of a node from a different document tree, but does not
support a document fragment as $root.

createElement

$element = $dom->createElement( $nodename );

This function creates a new Element Node bound to the DOM with the name $nodename.

createElementNS

$element = $dom->createElementNS( $namespaceURI, $nodename );

This function creates a new Element Node bound to the DOM with the name $nodename and placed in the given namespace.

createTextNode

$text = $dom->createTextNode( $content_text );

As an equivalent of createElement, but it creates a Text Node bound to the DOM.

createComment

$comment = $dom->createComment( $comment_text );

As an equivalent of createElement, but it creates a Comment Node bound to the DOM.

createAttribute

$attrnode = $doc->createAttribute($name [,$value]);

Creates a new Attribute node.

createAttributeNS

$attrnode = $doc->createAttributeNS( namespaceURI, $name [,$value] );

Creates an Attribute bound to a namespace.

createDocumentFragment

$fragment = $doc->createDocumentFragment();

This function creates a DocumentFragment.

createCDATASection

$cdata = $dom->createCDATASection( $cdata_content );

Similar to createTextNode and createComment, this function creates a
CDataSection bound to the current DOM.

createProcessingInstruction

my $pi = $doc->createProcessingInstruction( $target, $data );

create a processing instruction node.

Since this method is quite long one may use its short form createPI().

createEntityReference

my $entref = $doc->createEntityReference($refname);

If a document has a DTD specified, one can create entity references by using
this function. If one wants to add a entity reference to the document, this
reference has to be created by this function.

An entity reference is unique to a document and cannot be passed to other
documents as other nodes can be passed.

NOTE: A text content containing something that looks like an entity reference, will
not be expanded to a real entity reference unless it is a predefined entity

This function creates and adds an internal subset to the given document.
Because the function automatically adds the DTD to the document there is no
need to add the created node explicitly to the document.

This function is similar to createInternalSubset() but this DTD is considered to be external and is therefore not added to the
document itself. Nevertheless it can be used for validation purposes.

importNode

$document->importNode( $node );

If a node is not part of a document, it can be imported to another document. As
specified in DOM Level 2 Specification the Node will not be altered or removed
from its original document ($node->cloneNode(1) will get called implicitly).

NOTE: Dont try to use importNode() to import sub-trees that contain an entity
reference - even if the entity reference is the root node of the sub-tree. This
will cause serious problems to your program. This is a limitation of libxml2
and not of XML::LibXML itself.

adoptNode

$document->adoptNode( $node );

If a node is not part of a document, it can be imported to another document. As
specified in DOM Level 3 Specification the Node will not be altered but it will
removed from its original document.

After a document adopted a node, the node, its attributes and all its
descendants belong to the new document. Because the node does not belong to the
old document, it will be unlinked from its old location first.

NOTE: Dont try to adoptNode() to import sub-trees that contain entity references -
even if the entity reference is the root node of the sub-tree. This will cause
serious problems to your program. This is a limitation of libxml2 and not of
XML::LibXML itself.

externalSubset

my $dtd = $doc->externalSubset;

If a document has an external subset defined it will be returned by this
function.

NOTE Dtd nodes are no ordinary nodes in libxml2. The support for these nodes in
XML::LibXML is still limited. In particular one may not want use common node
function on doctype declaration nodes!

internalSubset

my $dtd = $doc->internalSubset;

If a document has an internal subset defined it will be returned by this
function.

NOTE Dtd nodes are no ordinary nodes in libxml2. The support for these nodes in
XML::LibXML is still limited. In particular one may not want use common node
function on doctype declaration nodes!

setExternalSubset

$doc->setExternalSubset($dtd);

EXPERIMENTAL!

This method sets a DTD node as an external subset of the given document.

setInternalSubset

$doc->setInternalSubset($dtd);

EXPERIMENTAL!

This method sets a DTD node as an internal subset of the given document.

removeExternalSubset

my $dtd = $doc->removeExternalSubset();

EXPERIMENTAL!

If a document has an external subset defined it can be removed from the
document by using this function. The removed dtd node will be returned.

removeInternalSubset

my $dtd = $doc->removeInternalSubset();

EXPERIMENTAL!

If a document has an internal subset defined it can be removed from the
document by using this function. The removed dtd node will be returned.

getElementsByTagName

my @nodelist = $doc->getElementsByTagName($tagname);

Implements the DOM Level 2 function

In SCALAR context this function returns an XML::LibXML::NodeList object.

getElementsByTagNameNS

my @nodelist = $doc->getElementsByTagNameNS($nsURI,$tagname);

Implements the DOM Level 2 function

In SCALAR context this function returns an XML::LibXML::NodeList object.

getElementsByLocalName

my @nodelist = $doc->getElementsByLocalName($localname);

This allows the fetching of all nodes from a given document with the given
Localname.

In SCALAR context this function returns an XML::LibXML::NodeList object.

getElementById

my $node = $doc->getElementById($id);

Returns the element that has an ID attribute with the given value. If no such
element exists, this returns undef.

Note: the ID of an element may change while manipulating the document. For
documents with a DTD, the information about IDattributes is only available ifDTD loading/validation has been requested. For HTML documents parsed with the
HTML parser ID detection is done automatically. In XML documents, all xml:id
attributes are considered to be of type ID. You can test ID-ness of an
attribute node with $attr->isId().

In versions 1.59 and earlier this method was called getElementsById() (plural)
by mistake. Starting from 1.60 this name is maintained as an alias only for
backward compatibility.

indexElements

$dom->indexElements();

This function causes libxml2 to stamp all elements in a document with their
document position index which considerably speeds up XPath queries for large
documents. It should only be used with static documents that wont be further
changed by any DOM methods, because once a document is indexed, XPath will
always prefer the index to other methods of determining the document order of
nodes. XPath could therefore return improperly ordered node-lists when applied
on a document that has been changed after being indexed. It is of course
possible to use this method to re-index a modified document before using it
with XPath again. This function is not a part of the DOM specification.

This function returns number of elements indexed, -1 if error occurred, or -2
if this feature is not available in the running libxml2.